This invention relates to molded plastic products and more particularly to a method for manufacturing such products that include a structural load support insert member with functional openings therein which are covered by a film layer and wherein the film layer serves to prevent the escape of material during formation of a layer of polyurethane foam on the insert.
In the past it has been recognized that it is desirable to cover a load support or insert member in a composite plastic product with a film to prevent the escape of material through the insert during a foaming process in which polyurethane material is foamed with respect to the insert.
One such method is set forth in U.S. Pat. No. 4,228,115 issued Oct. 14, 1980 to Gardner for Method of Making a Horn Pad. In this method a horn switch assembly is covered by a plastic film and then the assembly is foamed to form a plastic product with a load support insert, a covering film and a layer of urethane foam. While suitable for its intended purpose, the method of the '115 patent requires that the inserts be fabricated as separate components used in a second manufacturing step which covers the insert with the film and ten moves the "covered insert" to the mold to carry out a foam operation.
U.S. Pat. Nos. 4,420,447 and 4,477,504 both disclose instrument panel constructions and methods for foaming material with respect to a load support insert which is covered by a film to prevent the escape of foam through operative openings in the insert member. In both cases, however, the insert is formed in a first manufacturing step and then the part is covered by film in a second manufacturing step to produce the subassembly used in a subsequent foaming step.